A femtocell is a small cellular base station that provides a mobile communication service in a comparatively narrow area. The femtocell has various advantages of expanding indoor service coverage, improving service quality, and effectively providing various wired and wireless integrated services. In addition, the femtocell has low installation and maintenance fees. Further, the femtocell can be installed in any location where an Internet channel is available.
One of the main purposes of introducing a femtocell is to distribute network load in a macrocell and to increase service capacity of the macrocell. For example, a plurality of femtocells may be installed within a service area of a macrocell in order to overcome a shortage in the service capacity of a macrocell. Since multiple femtocells are installed within a single macrocell, the femtocells, however, may cause a frequency interference problem, known as femtocell interference.
Furthermore, femtocells may be allocated with the same identification codes. Each base station is allocated an identification code in order for the base station to be distinguished from other base stations. For efficient system management, only a limited number of identification codes is available. Most of the available identification codes are allocated to macrocell base stations first, and only the few remaining identification codes may be allocated to femtocell base stations. Due to a shortage of identification codes, the same identification codes may be reused for multiple femtocell base stations installed in a service area of a macrocell. Such duplication of identification codes may cause a failure of the inter-cell handover from a macrocell base station to a femtocell base station. For example, when a handover procedure is performed from a macrocell to a femtocell, a target femtocell base station may not be distinguishable from other femtocell base stations. Particularly, when a target femtocell base station has the same identification code of other base station, the handover procedure may fail.
Such a failure in handover may also cause serious frequency interference problems. Such frequency interference problems may degrade the service quality of the overall communication network and deteriorate the load distribution effect of femtocell.